Unable to send this e-mail domain ( XXXXX ) has been black listed due to spam or forgery

We were getting the following error message when sending to a gmail account. The message got returned also went to spam mailbox. Web Hosting is “hostgator.com”. This is a online store using Prestashop, and the email we used was a gmail as well:

SMTP error from remote mail server after MAIL FROM::
host gateway.websitewelcome.com [74.52.223.18]:
553 5.5.4 I was unable to send this e-mail because the domain ( gmail.com ) has been black listed due to spam or forgery v2.